The invention relates to finding novel compounds having valuable properties, in particular those which can be used for the preparation of medicaments.
The present invention, in one aspect, relates to compounds which inhibit, regulate and/or modulate tyrosine kinase signal transduction, to compositions which comprise these compounds, and to methods for the use thereof for the treatment of tyrosine kinase-dependent diseases and conditions, such as cancer, tumour growth, arteriosclerosis, age-related macular degeneration, diabetic retinopathy, inflammatory diseases and the like, in mammals.
Tyrosine kinases are a class of enzymes which catalyse the transfer of the terminal phosphate of adenosine triphosphate to tyrosine residues in protein substrates. It is thought that tyrosine kinases, through substrate phosphorylation, play a crucial role in signal transduction for a number of cell functions. Although the precise mechanisms of signal transduction are still unclear, tyrosine kinases have been shown to be important contributing factors in cell proliferation, carcinogenesis and cell differentiation. Tyrosine kinases can be categorised as receptor-type tyrosine kinases or non-receptor type tyrosine kinases. Receptor-type tyrosine kinases have an extracellular portion, a transmembrane portion and an intracellular portion, while non-receptor type tyrosine kinases are exclusively intracellular.
Receptor-type tyrosine kinases contains a multiplicity of transmembrane receptors with different biological activity. Thus, about 20 different sub-families of receptor-type tyrosine kinases have been identified. One tyrosine kinase subfamily, known as the HER subfamily, contains EGFR, HER2, HER3 and HER4. Ligands from this subfamily of receptors include epithelial growth factor, TGF-α, amphiregulin, HB-EGF, betacellulin and heregulin. Another subfamily of these receptor-type tyrosine kinases is the insulin subfamily, which includes INS-R, IGF-IR and IR-R. The PDGF subfamily includes the PDGF-α and -β receptors, CSFIR, c-kit and FLK-II. In addition, there is the FLK family, which contains the kinase insert domain receptor (KDR), foetal liver kinase-1 (FLK-1), foetal liver kinase-4 (FLK-4) and the fms tyrosine kinase-1 (flt-1). The PDGF and FLK families are usually discussed together due to the similarities between the two groups. For a detailed discussion of receptor-type tyrosine kinases, see Plowman et al., DN & P 7(6):334-339, 1994, which is hereby incorporated by way of reference.
The non-receptor type tyrosine kinases likewise contain a multiplicity of subfamilies, including Src, Frk, Btk, Csk, Abl, Zap70, Fes/Fps, Fak, Jak, Ack and LIMK. Each of these subfamilies is further sub-divided into different receptors. For example, the Src subfamily is one of the largest subfamilies. It includes Src, Yes, Fyn, Lyn, Lck, Blk, Hck, Fgr and Yrk. The Src subfamily of enzymes has been linked to oncogenesis. For a more detailed discussion of non-receptor type tyrosine kinases, see Bolen Oncogene, 8:2025-2031 (1993), which is hereby incorporated by way of reference.
Both receptor type tyrosine kinases and non-receptor type tyrosine kinases are involved in cellular signalling pathways leading to numerous pathogenic conditions, including cancer, psoriasis and hyperimmune responses.
It has been proposed that various receptor-type tyrosine kinases, and the growth factors binding to them, play a role in angiogenesis, although some may promote angiogenesis indirectly (Mustonen and Alitalo, J. Cell Biol. 129:895-898, 1995). One of these receptor-type tyrosine kinases is foetal liver kinase 1, also referred to as FLK-1. The human analogue of FLK-1 is the kinase insert domain-containing receptor KDR, which is also known as vascular endothelial cell growth factor receptor 2 or VEGFR-2, since it binds VEGF with high affinity. Finally, the murine version of this receptor has also been called NYK (Oelrichs et al., Oncogene 8(1):11-15, 1993). VEGF and KDR are a ligand-receptor pair which plays a vital role in the proliferation of vascular endothelial cells and the formation and sprouting of blood vessels, referred to as vasculogenesis and angiogenesis respectively.
Angiogenesis is characterised by excessive activity of vascular endothelial growth factor (VEGF). VEGF actually consists of a family of ligands (Klagsburn and D'Amore, Cytokine & Growth Factor Reviews 7:259-270, 1996). VEGF binds the high affinity membrane-spanning tyrosine kinase receptor KDR and the related fms-like tyrosine kinase-1, also known as Flt-1 or vascular endothelial cell growth factor receptor 1 (VEGFR-1). Cell culture and gene knockout experiments indicate that each receptor contributes to different aspects of angiogenesis. KDR mediates the mitogenic function of VEGF, whereas Flt-1 appears to modulate non-mitogenic functions, such as those associated with cellular adhesion. Inhibiting KDR thus modulates the level of mitogenic VEGF activity. In fact, tumour growth has been shown to be susceptible to the antiangiogenic effects of VEGF receptor antagonists (Kim et al., Nature 362, pp. 841-844, 1993).
Solid tumours can therefore be treated with tyrosine inhibitors since these tumours depend on angiogenesis for the formation of the blood vessels that are necessary to support their growth. These solid tumours include monocytic leukaemia, carcinomas of the brain, genito-urinary tract, lymphatic system, stomach, larynx and lung, including lung adenocarcinoma and small cell lung carcinoma. Further examples include carcinomas in which overexpression or activation of Raf-activating oncogenes (for example, K-Ras, Erb-B) is observed. Such carcinomas include pancreatic and breast carcinoma. Inhibitors of these tyrosine kinases are therefore suitable for the prevention and treatment of proliferative diseases caused by these enzymes.
The angiogenic activity of VEGF is not limited to tumours. VEGF accounts for the angiogenic activity produced in or near the retina in diabetic retinopathy. This vascular growth in the retina leads to visual degeneration culminating in blindness. Ocular VEGF mRNA and protein levels are elevated by conditions such as retinal vein occlusion in primates and decreased pO2 levels in mice that lead to neovascularisation. Intraocular injections of anti-VEGF monoclonal antibodies or VEGF receptor immunofusions inhibit ocular neovascularisation in both primate and rodent models. Irrespective of the cause of induction of VEGF in human diabetic retinopathy, inhibition of ocular VEGF is suitable for treating this disease.
Expression of VEGF is also significantly increased in hypoxic regions of animal and human tumours adjacent to areas of necrosis. In addition, VEGF is upregulated by the expression of the oncogenes Ras, Raf, Src and mutant p53 (all of which are relevant in combating cancer). Anti-VEGF monoclonal antibodies inhibit the growth of human tumours in nude mice. Although the same tumour cells continue to express VEGF in culture, the antibodies do not diminish their mitotic rate. Thus, tumour-derived VEGF does not function as an autocrine mitogenic factor. VEGF therefore contributes to tumour growth in vivo by promoting angiogenesis through its paracrine vascular endothelial cell chemotactic and mitogenic activities. These monoclonal antibodies also inhibit the growth of typically less well vascularised human colon carcinomas in athymic mice and decrease the number of tumours arising from inoculated cells.
The expression of a VEGF-binding construct of Flk-1, Flt-1, the mouse KDR receptor homologue truncated to eliminate the cytoplasmic tyrosine kinase domains but retaining a membrane anchor, virtually stops the growth of a transplantable glioblastoma in mice, presumably by the dominant negative mechanism of heterodimer formation with membrane-spanning endothelial cell VEGF receptors.
Embryonic stem cells, which normally grow as solid tumours in nude mice, do not produce detectable tumours if both VEGF alleles are knocked out. Taken together, these data indicate the role of VEGF in the growth of solid tumours. Inhibition of KDR or Flt-1 is involved in pathological angiogenesis, and these receptors are suitable for the treatment of diseases in which angiogenesis is part of the overall pathology, for example inflammation, diabetic retinal vascularisation, as well as various forms of cancer, since tumour growth is known to be dependent on angiogenesis (Weidner et al., N. Engl. J. Med., 324, pp. 1-8, 1991).
Angiopoietin 1 (Ang1), a ligand for the endothelium-specific receptor-type tyrosine kinase TIE-2, is a novel angiogenic factor (Davis et al., Cell, 1996, 87:1161-1169; Partanen et al., Mol. Cell Biol., 12:1698-1707 (1992); U.S. Pat. Nos. 5,521,073; 5,879,672; 5,877,020; and 6,030,831). The acronym TIE stands for “tyrosine kinase with Ig and EGF homology domains”. TIE is used for the identification of a class of receptor-type tyrosine kinases which are expressed exclusively in vascular endothelial cells and early haemopoietic cells. TIE receptor kinases are typically characterised by the presence of an EGF-like domain and an immunoglobulin (Ig)-like domain which consists of extracellular fold units stabilised by disulfide bridge bonds between the chains (Partanen et al. Curr. Topics Microbiol. Immunol., 1999, 237:159-172). In contrast to VEGF, which exerts its function during the early stages of vascular development, Ang1 and its receptor TIE-2 act during the later stages of vascular development, i.e. during vascular transformation (transformation relates to the formation of a vascular lumen) and maturing (Yancopoulos et al., Cell, 1998, 93:661-664; Peters, K. G., Circ. Res., 1998, 83(3):342-3; Suri et al., Cell 87, 1171-1180 (1996)).
Accordingly, it would be expected that inhibition of TIE-2 should interrupt the transformation and maturing of a new vascular system initiated by angiogenesis and should thus interrupt the angiogenesis process. Furthermore, inhibition at the kinase domain binding site of VEGFR-2 would block phosphorylation of tyrosine residues and serve to interrupt initiation of angiogenesis. It therefore follows that inhibition of TIE-2 and/or VEGFR-2 should prevent tumour angiogenesis and serve to slow or completely eliminate tumour growth.
Accordingly, treatment of cancer and other diseases associated with inappropriate angiogenesis are provided.
The present invention relates to methods for the regulation, modulation or inhibition of TIE-2 for the prevention and/or treatment of diseases associated with unregulated or disturbed TIE-2 activity. In particular, the compounds according to the invention can also be employed in the treatment of certain forms of cancer. Furthermore, the compounds according to the invention can be used to provide additive or synergistic effects in certain existing cancer chemotherapies and/or can be used to restore the efficacy of certain existing cancer chemotherapies and radiotherapies.
The present invention furthermore relates to the compounds as inhibitors of Raf kinases.
Protein phosphorylation is a fundamental process for the regulation of cellular functions. The coordinated action of both protein kinases and phosphatases controls the degrees of phosphorylation and, hence, the activity of specific target proteins. One of the predominant roles of protein phosphorylation is in signal transduction, where extracellular signals are amplified and propagated by a cascade of protein phosphorylation and dephosphorylation events, for example in the p21ras/Raf pathway.
The p21ras gene was discovered as an oncogene of the Harvey (H-Ras) and Kirsten (K-Ras) rat sarcoma viruses. In humans, characteristic mutations in the cellular Ras gene (c-Ras) have been associated with many different types of cancers. These mutant alleles, which render Ras constitutively active, have been shown to transform cells, such, for example, as the murine cell line NIH 3T3, in culture.
The p21ras oncogene is a major contributor to the development and progression of human solid carcinomas and is mutated in 30% of all human carcinomas (Bolton et al. (1994) Ann. Rep. Med. Chem., 29, 165-74; Bos. (1989) Cancer Res., 49, 4682-9). In its normal, unmutated form, the Ras protein is a key element of the signal transduction cascade directed by growth factor receptors in almost all tissues (Avruch et al. (1994) Trends Biochem. Sci., 19, 279-83).
Biochemically, Ras is a guanine nucleotide binding protein, and cycling between a GTP-bound activated and a GDP-bound resting form is strictly controlled by Ras endogenous GTPase activity and other regulatory proteins. The Ras gene product binds to guanine triphosphate (GTP) and guanine diphosphate (GDP) and hydrolyses GTP to GDP. Ras is active in the GTP-bound state. In the Ras mutants in cancer cells, the endogenous GTPase activity is reduced and the protein consequently transmits constitutive growth signals to downstream effectors, such as, for example, the enzyme Raf kinase. This leads to the cancerous growth of the cells which carry these mutants (Magnuson et al. (1994) Semin. Cancer Biol., 5, 247-53). The Ras proto-oncogene requires a functionally intact c-Raf-1 proto-oncogene in order to transduce growth and differentiation signals initiated by receptor and non-receptor-type tyrosine kinases in higher eukaryotes.
Activated Ras is necessary for the activation of the c-Raf-1 proto-oncogene, but the biochemical steps through which Ras activates the Raf-1 protein (Ser/Thr) kinase are now well characterised. It has been shown that inhibiting the effect of active Ras by inhibiting the Raf kinase signalling pathway by administration of deactivating antibodies to Raf kinase or by co-expression of dominant negative Raf kinase or dominant negative MEK (MAPKK), the substrate of Raf kinase, leads to reversion of transformed cells to the normal growth phenotype, see: Daum et al. (1994) Trends Biochem. Sci., 19, 474-80; Fridman et al. (1994) J Biol. Chem., 269, 30105-8. Kolch et al. (1991) Nature, 349, 426-28 and for a review Weinstein-Oppenheimer et al. Pharm. & Therap. (2000), 88, 229-279.
Similarly, inhibition of Raf kinase (by antisense oligodeoxynucleotides) has been correlated in vitro and in vivo with inhibition of the growth of a variety of human tumour types (Monia et al., Nat. Med. 1996, 2, 668-75).
Raf serine- and threonine-specific protein kinases are cytosolic enzymes that stimulate cell growth in a variety of cell systems (Rapp, U. R., et al. (1988) in The Oncogene Handbook; T. Curran, E. P. Reddy and A. Skalka (eds.) Elsevier Science Publishers; The Netherlands, pp. 213-253; Rapp, U. R., et al. (1988) Cold Spring Harbor Sym. Quant. Biol. 53:173-184; Rapp, U. R., et al. (1990) Inv Curr. Top. Microbiol. Immunol. Potter and Melchers (eds.), Berlin, Springer-Verlag 166:129-139).
Three isozymes have been characterised:
C-Raf (Raf-1) (Bonner, T. I., et al. (1986) Nucleic Acids Res. 14:1009-1015). A-Raf (Beck, T. W., et al. (1987) Nucleic Acids Res. 15:595-609) and B-Raf (Qkawa, S., et al. (1998) Mol. Cell. Biol. 8:2651-2654; Sithanandam, G. et al. (1990) Oncogene:1775). These enzymes differ in their expression in various tissues. Raf-1 is expressed in all organs and in all cell lines that have been examined, and A- and B-Raf are expressed in urogenital and brain tissues respectively (Storm, S. M. (1990) Oncogene 5:345-351).
Raf genes are proto-oncogenes: they can initiate malignant transformation of cells when expressed in specifically altered forms. Genetic changes that lead to oncogenic activation generate a constitutively active protein kinase by removal of or interference with an N-terminal negative regulatory domain of the protein (Heidecker, G., et al. (1990) Mol. Cell. Biol. 10:2503-2512; Rapp, U. R., et al. (1987) in Oncogenes and Cancer; S. A. Aaronson, J. Bishop, T. Sugimura, M. Terada, K. Toyoshima and P. K. Vogt (eds.) Japan Scientific Press, Tokyo). Microinjection into NIH 3T3 cells of oncogenically activated, but not wild-type, versions of the Raf protein prepared with Escherichia coli expression vectors results in morphological transformation and stimulates DNA synthesis (Rapp, U. R., et al. (1987) in Oncogenes and Cancer; S. A. Aaronson, J. Bishop, T. Sugimura, M. Terada, K. Toyoshima and P. K. Vogt (ed.) Japan Scientific Press, Tokyo; Smith, M. R., et al. (1990) Mol. Cell. Biol. 10:3828-3833).
Consequently, activated Raf-1 is an intracellular activator of cell growth. Raf-1 protein serine kinase is a candidate for the downstream effector of mitogen signal transduction, since Raf oncogenes overcome growth arrest resulting from a block of cellular Ras activity due either to a cellular mutation (Ras revertant cells) or microinjection of anti-Ras antibodies (Rapp, U. R., et al. (1988) in The Oncogene Handbook, T. Curran, E. P. Reddy and A. Skalka (ed.), Elsevier Science Publishers; The Netherlands, pp. 213-253; Smith, M. R., et al. (1986) Nature (London) 320:540-543).
C-Raf function plays a role in the transformation by a variety of membrane-bound oncogenes and in the growth stimulation by mitogens contained in serums (Smith, M. R., et al. (1986) Nature (London) 320:540-543). Raf-1 protein serine kinase activity is regulated by mitogens via phosphorylation (Morrison, D. K., et al. (1989) Cell 58:648-657), which also effects sub-cellular distribution (Olah, Z., et al. (1991) Exp. Brain Res. 84:403; Rapp, U. R., et al. (1988) Cold Spring Harbor Sym. Quant. Biol. 53:173-184. Raf-1 activating growth factors include platelet-derived growth factor (PDGF) (Morrison, D. K., et al. (1988) Proc. Natl. Acad. Sci. USA 85:8855-8859), colony-stimulating factor (Baccarini, M., et al. (1990) EMBO J. 9:3649-3657), insulin (Blackshear, P. J., et al. (1990) J. Biol. Chem. 265:12115-12118), epidermal growth factor (EGF) (Morrison, R. K., et al. (1988) Proc. Natl. Acad. Sci. USA 85:8855-8859), interleukin-2 (Turner, B. C., et al. (1991) Proc. Natl. Acad. Sci. USA 88:1227) and interleukin-3 and granulocyte macrophage colony-stimulating factor (Carroll, M. P., et al. (1990) J. Biol. Chem. 265:19812-19817).
After mitogen treatment of cells, the transiently activated Raf-1 protein serine kinase translocates to the perinuclear area and the nucleus (Olah, Z., et al. (1991) Exp. Brain Res. 84:403; Rapp, U. R., et al. (1988) Cold Spring Harbor Sym. Quant. Biol. 53:173-184). Cells containing activated Raf are altered in their pattern of gene expression (Heidecker, G., et al. (1989) in Genes and signal transduction in multistage carcinogenesis, N. Colburn (ed.), Marcel Dekker, Inc., New York, pp. 339-374) and Raf oncogenes activate transcription from Ap-I/PEA3-dependent promoters in transient transfection assays (Jamal, S., et al. (1990) Science 344:463-466; Kaibuchi, K., et al. (1989) J. Biol. Chem. 264:20855-20858; Wasylyk, C., et al. (1989) Mol. Cell. Biol. 9:2247-2250).
There are at least two independent pathways for Raf-1 activation by extracellular mitogens: one involving protein kinase C (KC) and a second initiated by protein tyrosine kinases (Blackshear, P. J., et al. (1990) J. Biol. Chem. 265:12131-12134; Kovacina, K. S., et al. (1990) J. Biol. Chem. 265:12115-12118; Morrison, D. K., et al. (1988) Proc. Natl. Acad. Sci. USA 85:8855-8859; Siegel, J. N., et al. (1990) J. Biol. Chem. 265:18472-18480; Turner, B. C., et al. (1991) Proc. Natl. Acad. Sci. USA 88:1227). In each case, activation involves Raf-1 protein phosphorylation. Raf-1 phosphorylation may be a consequence of a kinase cascade amplified by autophosphorylation or may be caused entirely by autophosphorylation initiated by binding of a putative activating ligand to the Raf-1 regulatory domain, analogous to PKC activation by diacylglycerol (Nishizuka, Y. (1986) Science 233:305-312).
One of the principal mechanisms by which cellular regulation is effected is through the transduction of extracellular signals across the membrane that in turn modulate biochemical pathways within the cell. Protein phosphorylation represents one course by which intracellular signals are propagated from molecule to molecule resulting finally in a cellular response. These signal transduction cascades are highly regulated and often overlapping, as evident from the existence of many protein kinases as well as phosphatases. Phosphorylation of proteins occurs predominantly at serine, threonine or tyrosine residues, and protein kinases have therefore been classified by their specificity of phosphorylation site, i.e. serine/threonine kinases and tyrosine kinases. Since phosphorylation is such a ubiquitous process within cells and since cellular phenotypes are largely influenced by the activity of these pathways, it is currently believed that a number of disease states and/or diseases are attributable to either aberrant activation or functional mutations in the molecular components of kinase cascades. Consequently, considerable attention has been devoted to the characterisation of these proteins and compounds that are able to modulate their activity (for a review see: Weinstein-Oppenheimer et al. Pharma. &. Therap., 2000, 88, 229-279).
The protein kinase PKB (also known as AKT and RAC-PK) is a member of the AKT/PKB family of serine/threonine kinases and has been shown to be involved in a diverse set of signalling pathways in human malignancy (Nicholson et al., Cell. Signal., 2002, 14, 381-395). PKB, like other members of the AKT/PKB family, is located in the cytosol of unstimulated cells and translocates to the cell membrane following stimulation. PKB translocation can be activated by a number of ligands, including platelet derived growth factor, epidermal growth factor, basic fibroblast growth factor, cellular stress, such as, for example, heat shock and hyperosmolarity, as well as insulin (Bos, Trends Biochem. Sci., 1995, 20, 441-442), and other studies have shown that this activation is through PI3 kinase which is wortmannin sensitive (Franke et al., Science, 1997, 275, 665-668). Once localised to the plasma membrane, PKB has been shown to mediate several functions within the cell, including apoptosis, the metabolic effects of insulin, induction of differentiation and/or proliferation, protein synthesis and stress responses (Alessi and Cohen, Curr. Opin. Genet. Dev., 1998, 8, 55-62; Downward, Curr. Opin. Cell Biol., 1998, 10, 262-267).
PKB was cloned independently in 1991 by three groups (Bellacosa et al., Science, 1991, 254, 274-277; Coffer and Woodgett, Eur. J. Biochem., 1991, 201, 475-481; Jones et al., Cell Regul., 1991, 2, 1001-1009), but its association with primary human gastric carcinoma was recognised as early as 1987 (Staal et al., Proc. Natl. Acad. Sci. USA, 1987, 84, 5034-5037). Sequencing of PKBα revealed homology within the kinase domains to the PKA (about 68%) and PKC isozymes (about 73%) (Jones et al., Proc. Natl. Acad. Sci. U.S.A., 1991, 88, 4171-5), a fact that lead to its renaming as PKB. There are three cellular isoforms of PKB and two splice variants (PKBAα, β, γ,β1, γ1; Brazil et al. Trends in Bio Sci, 2001, 26, 657-663). PKBα was found to be amplified or overexpressed in gastric adenocarcinomas and in a breast cancer cell line (Staal et al., Proc. Natl. Acad. Sci. U.S.A., 1987, 84, 5034-7; Jones et al., Cell Regul., 1991, 2, 1001-9). PKBβ is amplified or overexpressed in 3% of breast (Bellacosa et al., Int. J. Cancer, 1995 64, 280-5), 12% of pancreatic (Cheng et al., Proc. Natl. Acad. Sci. U.S.A., 1996, 93, 3636-41) and 15% of ovarian cancers (Bellacosa et al., Int. J. Cancer, 1995, 64, 280-5; Cheng et al., Proc. Natl. Acad. Sci. U.S.A., 1992, 89, 9267-71).
PKBγ is overexpressed in oestrogen receptor-deficient breast cancer and in androgen-independent prostate cell lines (Nakatani et al., J. Biol. Chem. 1999, 274, 21528-32).
It has been proposed that PKB is a gene which is involved in chromosomal rearrangement at chromosome band 14q32. This locus is known to undergo rearrangement in human T-cell malignancies, such as, for example, prolymphocytic leukaemias and mixed lineage childhood leukaemias (Staal et al., Genomics, 1988, 2, 96-98).
PKB also plays a role in the prevention of “programmed cell death” or apoptosis by inhibitory phosphorylation of ASK-1, Bad, Caspase9 and FKHR (for review see Nicholson et al., Cell Signalling 2001, 14, 281-395). It has been shown that PKB provides a survival signal (for review see Lawlor et al., J. of Cell Science 2001, 114, 2903-2910) to cells in order to protect them from a number of agents, including UV radiation (Dudek et al., Science, 1997, 275, 661-665), withdrawal of IGF1 from neuronal cells, detachment from the extracellular matrix, stress and heat shock (Alessi and Cohen, Curr. Opin. Genet. Dev., 1998, 8, 55-62).
The dual-specific phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome ten) increases the PtdIns(3, 4, 5)P3 level in the cell by dephosphorylation of PtdIns(3, 4, 5)P3. PtdIns(3, 4, 5)P3 binds to the PH domain (Pleckstrin homology domain) of PKB. This binding is an important for membrane translocation and activation of PKB. PTEN is a tumour suppressor gene mutated in a large proportion of glioblastoma and melanoma cell lines, advanced prostate carcinomas and endometrial carcinomas. Furthermore, it is deleted in >80% of patients with hereditary conditions, such as, for example, Cowden's disease, Lhermitte-Duclose disease and Bannayan-Zonana Syndrome. The patients display a number of similar features, including multiple benign tumours (harmatomas) and increased susceptibility to breast and thyroid malignancies (Di Cristofano et al. Cell, 2000, 100, 387-390).
Cell lines derived from PTEN+/− heterozygous mice (PTEN−/− heterozygous mice are not viable) show increased PtdIns(3, 4, 5)P3 levels paralleled by increased PKB activity, with concomitant decreased sensitivity to apoptosis (Di Christofano et al. Nat. Genet. 1998, 19, 348-355; Stambolic et al., Cell, 1998, 95, 29-39, Myers et al., Proc. Natl. Acad. Si. U.S.A., 1998, 96 13513-13518).
PKB is also able to promote cell cycle progression by inhibiting p21 cell cycle inhibitor (Zhou et al.; Nat. Cell Biol., 2002, 3, 245-252).
These findings may explain the overexpression of PKB observed in cancer cells which allows preferential survival and proliferation of the carcinomas by avoiding the normal progression to apoptosis.
At present, there are no known therapeutic agents which effectively inhibit the activity of PKB. Consequently, there remains a long felt need for additional agents which are capable of effectively inhibiting PKB function for the activation of pro-apoptotic proteins in all kinds of cancer as chemotherapeutic agents.
The identification of small compounds which specifically inhibit, regulate and/or modulate signal transduction of tyrosine kinases, in particular TIE-2 and/or Raf kinases, is therefore desirable and an aim of the present invention.
It has been found that the compounds of the formula I and salts thereof have very valuable pharmacological properties while being well tolerated. In particular, they exhibit tyrosine kinase and in particular TIE-2 inhibiting properties.
The compounds according to the invention are, in addition, suitable as food supplements, for the treatment of diseases and/or dysfunctions which are characterised by oxidative stress conditions and as sunscreens in cosmetic formulations.